These sheets of commemorative national park stamps are produced yearly. Each stamp includes a full-color photograph of ten national park areas and information about their importance. Stamps may be placed in the designated area in the Passport book (see below for more information). The 1994 series features the following National Park Service areas: Martin Van Buren National Historic Site, Allegheny Portage Railroad National Historic Site, Vietnam Veterans Memorial, Carl Sandburg Home National Historic Site, Golden Spike National Historic Site, Harry S Truman National Historic Site, Lyndon B. Johnson National Historical Park, Florissant Fossil Bends National Monument, Organ Pipe Cactus National Monument, and Kenai Fjords National Park.